1. Field of the Invention
The present invention generally relates to refrigerant compressors, and more particularly relates to suction accumulators used in conjunction with refrigerant compressors.
2. Description of the Related Art
Air conditioning and refrigeration systems in use today include a compressor that compresses and superheats refrigerant vapor, which is then run through a condenser, expanded, and evaporated in turn before returning to the compressor to begin the cycle again. The output of the evaporator carries components of refrigerant and lubricating oil in a vapor-liquid mixture. In some cases, a suction accumulator is interposed between the evaporator and the compressor. Primarily, the accumulator receives and accumulates the gas-liquid mixture from the evaporator outlet and serves as a reservoir and separator in which liquid collects at the bottom and gas at the top.
The basic structure of a suction accumulator is typically a cylindrical reservoir formed from one or more portions and having top and bottom ends. The top end portion typically is manufactured from a material having superior plasticity characteristics, such as copper, and is most often convex or frusto-conical in shape. The top end portion also has an inlet aperture to accommodate an inlet tube, also typically made from copper, for the connection of the suction accumulator to the output conduit of the evaporator. The bottom end portion has an outlet aperture to accommodate a suction tube which is partially internal to the accumulator reservoir and has one end connected to the compressor and an open end located inside the accumulator reservoir, above the level of the liquid, so that the compressor draws primarily gas through the suction tube, Typically, a small bleed hole is located on the return suction tube to effect a suction pressure near the bottom end of the accumulator reservoir thereby aspirating the liquid accumulated therein.
Accumulators are typically mounted on the compressor housing. This reduces pressure drop in the connecting tubing, improves performance, and makes the refrigeration system compact and easy to manufacture. However, since the accumulator is mounted directly on the compressor housing, any vibration generated by the compressor can be transmitted to the accumulator. This vibration can stress the joints between the suction accumulator inlet and the evaporator output conduit and is sometimes sufficient to fatigue and damage the individual components. The maximum stress has been found near the input tube/top end input aperture joint and is a result of the combined load of the pressure pulsations and vibrations triggered by operation of the compressor and associated unit. The convex or frusto-conical shapes at the top end part of prior art suction accumulators were an effort to distribute the stress loads over a larger area and to prevent concentration of stress at the joint of the input suction tube and the inlet aperture at the top end part. Generally, such prior art convex or frusto-conical shaped top ends had to be manufactured from materials of superior plasticity, such as copper, to achieve the desired results.
One prior art arrangement for mounting accumulators in a refrigeration system is disclosed in U.S. Pat. No. 4,607,503, which shows an accumulator bracket disposed in the area between the accumulator casing and the compressor housing. While this bracket provides a reliable mount for the accumulator on the compressor, some vibration is transmitted to the accumulator. Moreover, this accumulator location permits use of the accumulator as a handle for the compressor during installation of the unit, which will sometimes result in damage to the return tubing.
Another prior art arrangement for mounting of accumulators is disclosed in U.S. Pat. No. 4,888,962, which is assigned to the assignee of the present invention and which discloses an accumulator assembly having strap means engaged with the compressor housing for holding the accumulator in closely spaced relationship with the housing. The strap means includes a spring loop formed thereon for resiliently varying the tension of the strap means so that the accumulator may be tightly held in close proximity to the compressor. Special self-tapping screws are necessary to tighten the accumulator strap and adjust its tension. This increases the total number of parts, time necessary for assembly of the accumulator, cost, and moreover, the metal area covered by the strap will not be painted beneath the strap.